In physiology, perfusion is the process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. Physiology (from Greek grc φύσις physis, "nature origin" and grc -λογία -logia) is the study of the mechanical physical Arteries are Blood vessels that carry blood away from the Heart. Blood is a specialized Bodily fluid that delivers necessary substances to the body's cells such as nutrients and oxygen—and transports Waste products Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Tissue is a cellular organizational level intermediate between cells and a complete organism The word is derived from the French verb "perfuser" meaning to "pour over or through. "
Tests of adequate perfusion are a part of patient triage performed by medical or emergency personnel in a mass casualty incident. Triage (ˈtriːɑːʒ is a process of prioritizing patients based on the severity of their condition so as to treat as many as possible when resources are insufficient for all Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the
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Calculation
Perfusion ("F") can be measured with the following formula, where Pa is mean arterial pressure, Pv is mean venous pressure, and R is vascular resistance: [1]
The term "Pa - Pv" is sometimes presented as "ΔP", for the change in pressure. The mean arterial pressure ( MAP) is a term used in medicine to describe a notional average Blood pressure in an individual Vascular resistance is a term used to define the resistance to flow that must be overcome to push Blood through the Circulatory system. [2]
The terms "perfusion" and "perfusion pressure" are sometimes used interchangeably, but the equation should make clear that resistance can have an effect on the perfusion, but not on the perfusion pressure.
Overperfusion and underperfusion
The terms "overperfusion" and "underperfusion" are measured relative to the average level of perfusion across all tissues in an individual body, and the terms should not be confused with hypoperfusion and "hyperperfusion", which measure the perfusion level to the tissue's current need. In Medicine, ischemia ( Greek ισχαιμία, isch- is restriction hema or haema is Blood) is a restriction
Tissues like the skin are considered overperfused and receive more blood than would be expected to meet the metabolic needs of the tissue. The skin is the outer covering of living tissue of an animal (or plant In the case of the skin, extra blood flow is used for thermoregulation. Thermoregulation is the ability of an Organism to keep its body temperature within certain boundaries even when temperature surrounding is very different In addition to delivering oxygen, the blood helps dissipate heat by redirecting warm blood close to the surface where it can cool the body through the sweating and thermal radiation. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the In Physics, dissipation embodies the concept of a Dynamical system where important mechanical modes such as Waves or Oscillations lose Energy Thermal radiation is Electromagnetic radiation emitted from the surface of an object which is due to the object's Temperature.
Measurement using fMRI
Two main categories of functional magnetic resonance imaging (fMRI) techniques can be used to measure tissue perfusion in vivo. Functional MRI or functional Magnetic Resonance Imaging (fMRI is a type of specialized MRI scan In vivo ( Latin: within the living means that which takes place inside an organism.
- The first is based on the use of injected contrast agent that changes the magnetic susceptibility of blood and thereby the MR signal which is repeatedly measured during bolus passage. Contrast medium Radiocontrast agents (also simply contrast agents or contrast materials) are compounds used to improve the visibility of internal bodily structures In Electromagnetism the magnetic susceptibility ( Latin: susceptibilis “receptiveness” is the degree of Magnetization of a material in response In medicine a bolus (from Latin bolus, ball is the administration of a Medication, Drug or other compound that is given to raise
- The other category is based on arterial spin labeling (ASL), where arterial blood is magnetically tagged before it enters into the tissue of interest and the amount of labeling is measured and compared to a control recording obtained without spin labeling. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field.
See also
References
- ^ Richard E. Reperfusion injury refers to damage to tissue caused when Blood supply returns to the tissue after a period of Ischemia. Klabunde. Cardiovascular Physiology Concepts. Retrieved on 9/12/06.
- ^ Physiology at MCG 7/7ch04/7ch04p26 - "Renal Perfusion Pressure and Vascular Resistance"
External links
The Medical College of Georgia, also known as MCG, is a public medical Research university located in downtown Augusta Georgia.Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic